Has anyone had my experience (tested & repeatable) that the live Lubuntu CD 10.04 & 10.10 trashes the boot NTFS sector. Just loading the CD is sufficient, I suspect it's related to Grub2 as it never happened with earlier versions, Jaunty is no problem. If general, this is a very serious malfunction. I wondered about having used a download from a bad source, but it also happens with a CD made from a reputable magazine DVD. I was checking it prior to giving it to someone to try on their old laptop on the lines "it's completely safe to try this, it doesn't write to your HD" whoops!.

Are you saying it has overwritten the master boot record, that you were booting with windows bootloader?

You'll need to be a lot more specific and detailed starting with putting the CD in the drive and booting from it. Exactly what you did and what the problem was. You weren't able to boot windows and??

I've installed Lubuntu several times in the last month without any problems.

I was in process of composing a long detailed answer but meanwhile,I didnt instal Lubuntu, just ran the live CD without changing any prompts as far as the normal desktop screen, then closed following the prompts. I have another check to complete, letting Win XP do a full format instead of quick, in the hope that the ghosts of previous partition tables will go away, but my worry is that running a live CD will reliably change the HD boot sector.Theres no trace of Lubuntu on the HDs

Don't see how that would be possible without some user input. Did you just boot the Lubuntu CD to the Desktop? What made you think your boot sector was trashed? What OS do you have on the machine?

I have seen the same behavior with a Knoppix-CD some years ago. I didn't do anything to the harddisk, but had to re-install the bootsector after rebooting. This was resolved in the next version, but I don't remember what has caused this behavior.

I have tracked down what is needed.
PC has 2 HDs. I used to use sda in partitions to run Ubuntu & Win XP and backups of partitions copied to sdb. After many years use I lost access to XP in Jan. after trying the Lubuntu live disk 10.10.
Test situation.Pentium4 3GHz with 2 x 250 GB SATA disks.
Sda with 2 NTFS partitions, only Win XP on sda1 (boot),just installed, ,sda2 empty and Ubuntu Lucid & grub1 on sdb,has been updated with each LTS version since Dapper, no bootable partition since earlier crashes.
With only sda connected Live Lubuntu 10.10 runs happily from a cd with no effect on the HD, just as Jaunty Ubuntu etc has always done. but I note that the HD light flashes while the CD is booting.
Restart with sdb connected, win Xp boots and Ubuntu Lucid on sdb1 can be booted using a super grub cd to find the original grub menu from menu.lst.
Live CD of jaunty boots with no ill effect.
Boot Lubuntu 10.10 from live CD (Iassume this differs in using grub2) HD light flashes on boot, but no more than when Jaunty Live CD boots.
Shut down: two dead sda NTFS partitions. Using Gparted, I find the ghost of previous partitions,the NTFS is now ext3 I didnt spend too much time trying to recover with testdisk,fdisk & gparted. Although sda1 partition size was correct changing the type from 83 to 07 didnt work.
I surmise that when Lubuntu loads,for some reason it finds the old details of partitioning possibly on sdb in the grub dir and writes it to sda1.
I really think that a live cd which may be used as a demo version should write nothing to the HD without asking for permission.
If anyone can advise on logging the Lubuntu live disk start up I'm happy to try to find the offending operation, otherwise I may as well have a proper clean reinstall & get out my backups.

The live CD doesn't even boot with grub (it uses isolinux; a live flashdrive should use syslinux). Not sure why it would be writing anything anywhere. Do you presently, or did you ever have a swap partition on sdb? If the live CD sees a partition as swap, it will use it.

yes there was a swap partition on sdb9, used by 10.04 sitting on sdb1.
I thought you might have identified the source of the bad disk data, but I have now cleared down sdb except for an ext3 partion containing 10.o4 ( it seems to run just as well with no swap partition, for test purposes at least). Unfortunately the problem with the live Lubuntu CD persists. Although I had done a full format of sda & only installed Win XP, when I rebooted after running the live CD , with only sda phyically connected there was grub with old details failing to boot.I had cloned the working sda1 winxp partition & the first 512 bytes of sda-. Restoring the first sector made the partition table look ok from Disk Utility & gparted, but it wasnt recognised by windows or Ubuntu till I copied back the partition but I am still suprised that only this particular version of live cd is troublesome. Its such a time consuming business and no one else seems to be troubled so I think its time to draw a line under this & keep awayfrom that Live CD. I would abandon XP altogether but I need it for Garmin Mapsource & a few other old programs

Prior to cloning, which bootloader were you using to boot xp, ntldr or grub?

What do you mean by "it wasn't recognized"? How were you checking? This was an empty drive with just the mbr as I understand your last post??

NTLDR
sda (250GB) was repartitioned with gparted to 2 NTFS partitions then reformatted with the winxp install disk -fullformat not just quick format & continued with XP install, with no sdb connected this booted in the normal XP way with NTLDR. To make cloning quicker I kept sda1 to 13GB , a big chunk as sda2 'sparewin' and left rest unpartitioned ('unallocated' in gparted).
Cloned 512 bytes to a memory stick file and sda1 to a spare PATA drive added for the purpose as a slave on the cd cable, using dd and booting from the reconnected sdb ubuntu drive.(the SATA drives sda & sdb got shifted to sdb & sdc with the empty PATA sdive becoming sda, so I had to boot with a supergrub disk to do this & exercise great care with the if & of parameters.) I think I succeeded in having an winXP drive devoid of any active traces of grub.

"Restoring the first sector made the partition table look ok from Disk Utility & gparted, but it wasnt recognised by windows or Ubuntu till I copied back the partition "

When I first had this problem, on about 2 of 6 times using supergrub 'restore windows boot' it worked, but other times not, sometimes using windows install it worked when there was a message like 'there is data on drive c continue ?', but usually it just offerred 'format'. Checking with Linux Disk manager, gparted fdisk & testdisk often showed different results on the same drive. Often Disk manager showed what looked like a usable sytem but it wouldnt mount.
About the only consistent thing is that loading the live CD with 10.04 on the slave drive stops the windows disk working. Loading the live CD with only the master (windowsXP) drive connected, no problem.
I'm getting better at recovering, but just restoring 13 GB takes time & checking & usually failing all the alternative methods is very time consuming - not a whinge but if no one else has this problem I will leave it until some other unfortunate posts with similar before getting into the fray again.
At least I understand more about bootsectors & info at start of partitions. I've been dual booting since Dapper in happy ignorance, with only very occasional recourse to supergrub to fix boot problems.